Methods of patterning photoresist, and methods of forming semiconductor constructions

ABSTRACT

The invention includes semiconductor constructions containing optically saturable absorption layers. An optically saturable absorption layer can be between photoresist and a topography, with the topography having two or more surfaces of differing reflectivity relative to one another. The invention also includes methods of patterning photoresist in which a saturable absorption layer is provided between the photoresist and a topography with surfaces of differing reflectivity, and in which the differences in reflectivity are utilized to enhance the accuracy with which an image is photolithographically formed in the photoresist.

RELATED PATENT DATA

This patent resulted from a continuation of U.S. patent application Ser.No. 11/341,201, which was filed Jan. 27, 2006, which issued as U.S. Pat.No. 7,432,197, and which is hereby incorporated herein by reference.

TECHNICAL FIELD

The invention pertains to semiconductor constructions, methods offorming semiconductor constructions, and methods of patterningphotoresist.

BACKGROUND OF THE INVENTION

Photolithography is commonly utilized to form microstructures, withexemplary microstructures being integrated circuit devices andMicro-Electro-Mechanical Systems (MEMS). Photolithography utilizespatterned electromagnetic radiation (typically ultraviolet light) tocreate a desired pattern in a photosensitive material (photoresist).

In typical processing, photoresist is coated on the substrate, andelectromagnetic radiation is passed through a patterned mask (typicallycalled a reticle) to form a pattern of exposed and unexposed regions ofthe photoresist. The photoresist is then developed to selectively removeeither the exposed or unexposed regions. If the exposed regions areremoved, the resist is referred to as a positive resist; and if theunexposed regions are removed, the resist is referred to as a negativeresist.

The patterned resist can subsequently be utilized as a sacrificial maskfor patterning layers underlying the resist. Alternatively, thepatterned photoresist can be a non-sacrificial material utilized as anelement of a microstructure.

A continuing goal is to decrease the dimensions of microstructures. Itis desired to form patterns in photoresist with ever-increasing accuracyas the desired sizes of microstructures continue to shrink, and this iscreating difficulties with present photolithographic techniques.

An exemplary application for photolithography is to form patterns inupper layers of materials that are desired to align with patterns inunderlying layers. For instance, in semiconductor manufacturing it isoften desired to establish vertically-extending electrical connectionbetween upper conductive structures and lower conductive structures. Asdevice dimensions decrease, this becomes an increasingly difficultchallenge. Alignment tolerances are now approaching nanometerdimensions.

At the tight tolerances of present-day manufacturing, misalignment ofphotolithographically-formed patterns in upper layers relative tostructures in lower layers is common, and accordingly numerousprocedures have been developed for addressing misalignment problems.

One method is to avoid photolithography, and to instead useself-aligned-contact methods where the selectivity of differentmaterials to different etch chemistries is used to pattern materials.Such methodology can be useful in particular circumstances, but createsproblems in developing appropriate etch chemistries, development times,and etching conditions.

Another method is to utilize methods of self-assembly at the molecularlevel so that devices assemble themselves in a predictable manner. Thistechnology holds promise, but is still in its infancy.

Yet another method is to use photolithography, but to enlarge thefeatures patterned in the photoresist so that the patterned area islarge enough to compensate for estimated amounts of misalignment. Thismethodology can alleviate misalignment-caused problems, and has beenutilized with a substantial degree of success. However, the methodologywastes valuable semiconductor real estate.

It is desired to develop new methods which can improve accuracy withwhich patterns are formed in photosensitive materials.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a method of patterningphotoresist. A construction is provided which has an optically saturableabsorption layer—also referred to as a layer of photo-bleachablematerial; or as a layer of contrast enhancement material (CEM)—over atopography with surfaces which differ in reflectivity relative to oneanother. Photoresist is formed over the optically saturable absorptionlayer. Electromagnetic radiation is directed into the photoresist. Someof the directed electromagnetic radiation passes through thephotoresist, to the topography, and then reflects back from thetopography to the photoresist. The difference in reflectivity of thesurfaces of the topography patterns the reflected electromagneticradiation. The directed electromagnetic radiation and patternedreflected electromagnetic radiation together expose a first portion ofthe photoresist to a threshold dose of radiation while a second portionof the photoresist remains not exposed to the threshold dose. Thephotoresist is then developed to selectively remove either the first orsecond portion of the photoresist relative to the other of the first andsecond portions.

In one aspect, the invention includes a method of patterning photoresistover a semiconductor construction. The semiconductor construction isprovided to have first and second regions, with the first region beingmore reflective than the second region. An optically saturableabsorption layer is formed over the first and second regions.Photoresist is formed over the optically saturable absorption layer.Electromagnetic radiation is reflected from the first region tooptically alter a segment of the optically saturable absorption layerbeneath the photoresist and thereby increase transparency of suchsegment. Electromagnetic radiation is directed into the photoresist.Some of the directed electromagnetic radiation passes through thephotoresist, bounces from the first region, through the altered segmentof the optically saturable absorption layer and into the photoresist.The directed electromagnetic radiation and bounced electromagneticradiation together expose a first portion of the photoresist to athreshold dose of radiation while a second portion of the photoresistremains not exposed to the threshold dose. The photoresist is thendeveloped to selectively remove either the first or second portion ofthe photoresist relative to the other the first and second portions.

In one aspect, the invention includes a method of forming asemiconductor construction. A semiconductor substrate is provided. Atleast one structure is formed over the semiconductor substrate, withsuch structure appearing in at least one cross-sectional view tocomprise spaced projections formed over the substrate. The spacedprojections have upper surfaces which are defined to be first surfaces.Regions between the spaced projections have upper surfaces which aredefined to the second surfaces. The first surfaces have greaterreflectivity than the second surfaces. A first layer is formed over thefirst and second surfaces. A second layer is formed over the firstlayer, with the second layer being an optically saturable absorptionlayer. Photoresist is formed over the optically saturable absorptionlayer. Electromagnetic radiation is reflected from the first surfaces tooptically alter a segment of the optically saturable absorption layerbeneath the photoresist and thereby increase transparency of suchsegment. Any electromagnetic radiation reflected from the secondsurfaces is insufficient to significantly alter transparency of theoptically saturable absorption layer. Electromagnetic radiation isdirected into the photoresist. Some of the directed electromagneticradiation passes through the photoresist, bounces from the firstsurfaces, through the altered segment of the optically saturableabsorption layer and into the photoresist. The directed electromagneticradiation and bounced electromagnetic radiation together expose a firstportion of the photoresist to a threshold dose of radiation while asecond portion of the photoresist remains not exposed to the thresholddose. The photoresist is developed to selectively removed either thefirst or second portion of the photoresist relative to the other of thefirst and second portions, and thereby form gaps in the photoresistselectively over designated regions comprising either the first surfacesor the second surfaces. The gaps are then extended through the first andsecond layers, and to the designated regions.

In one aspect, the invention includes a semiconductor construction. Suchconstruction comprises a semiconductor substrate. The constructionfurther comprises, in at least one cross-sectional view, spacedprojections over the substrate. Such projections are spaced from oneanother by an intervening region. A first layer is over the spacedprojections and over the intervening region between the spacedprojections. An optically saturable absorption layer is over the firstlayer, and photoresist is over the optically saturable absorption layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductor waferfragment at a preliminary processing stage of a method in accordancewith an exemplary aspect of the present invention.

FIG. 2 is a view of the fragment of FIG. 1 in an assembly utilized for aprocessing stage subsequent to that of FIG. 1.

FIG. 3 is a view of the assembly of FIG. 2 shown at a processing stagesubsequent to that of FIG. 2.

FIG. 4 is a view of the assembly of FIG. 2 shown at a processing stagesubsequent to that of FIG. 3.

FIG. 5 is a view of the assembly of FIG. 2 shown at a processing stagesubsequent to that of FIG. 4.

FIG. 6 is a view of the fragment of FIG. 1 shown at a processing stagesubsequent to that of FIG. 5.

FIG. 7 is a view of the fragment of FIG. 1 shown at a processing stagesubsequent to that of FIG. 6.

FIG. 8 is a view of the fragment of FIG. 1 shown at a processing stagesubsequent to that of FIG. 7.

FIG. 9 is a view of the fragment of FIG. 1 shown at a processing stagesubsequent to that of FIG. 8.

FIG. 10 is a view of the fragment of FIG. 1 shown at a processing stagesubsequent to that of FIG. 5 in accordance with an aspect of theinvention alternative to that shown in FIG. 6.

FIG. 11 is a diagrammatic, cross-sectional view of a semiconductor waferfragment shown at a processing stage analogous to that of FIG. 1 inaccordance with another aspect of the present invention.

FIG. 12 is a diagrammatic, cross-sectional view of a semiconductor waferfragment shown at a processing stage analogous to that of FIG. 1 inaccordance with yet another aspect of the present invention.

FIG. 13 is a view of the fragment of FIG. 12 shown at a processing stagesubsequent to that of FIG. 12.

FIG. 14 is a view of the fragment of FIG. 12 shown at a processing stagesubsequent to that of FIG. 13.

FIG. 15 is a view of the fragment of FIG. 12 shown at a processing stagesubsequent to that of FIG. 14.

FIG. 16 is a view of the fragment of FIG. 12 shown at a processing stagesubsequent to that of FIG. 15.

FIG. 17 is a view of the fragment of FIG. 12 shown at a processing stagesubsequent to that of FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

The invention includes aspects for improving photolithographicpatterning. In some aspects, radiation-reflective properties ofmaterials underlying a photoresist layer are utilized in conjunctionwith an optically saturable absorption layer to pattern electromagneticradiation during photolithographic patterning of the photoresist.Exemplary aspects of the invention are described with reference to FIGS.1-17.

Referring to FIG. 1, a semiconductor construction 10 is illustrated at apreliminary processing stage. The construction includes a substrate 12which can comprise any of various semiconductor materials, including,for example, monocrystalline silicon. In some aspects, substrate 12 cancomprise, consist essentially of, or consist of monocrystalline siliconlightly-doped with background p-type dopant. To aid in interpretation ofthe claims that follow, the terms “semiconductive substrate” and“semiconductor substrate” are defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove.

A pair of isolation regions 14 extend into the substrate, with suchisolation regions containing electrically insulative material 16. Theelectrically insulative material can, for example, comprise, consistessentially of, or consist of silicon dioxide. The isolation regions canbe any suitable isolation regions, and in some aspects will be shallowtrench isolation regions. The isolation regions have uppermost surfaces17 corresponding to uppermost surfaces of material 16.

A transistor 18 is supported by substrate 12. The transistor comprises agate stack 20 over the substrate, and conductively-doped source/drainregions 22 and 24 within the substrate and on opposing sides of the gatestack. The source/drain regions can be either majority n-type doped ormajority p-type doped, as will be recognized by persons of ordinaryskill in the art.

The gate stack 20 comprises gate dielectric 26, conductive gate material28, and an electrically insulative cap 30.

The gate dielectric 26 can comprise any suitable composition orcombination of compositions, and in particular aspects can comprise,consist essentially of, or consist of silicon oxide.

The conductive gate material 28 can comprise any suitable composition orcombination of compositions, and in some aspects can comprise, consistessentially of, or consist of one or more of various metals, metalcompositions, and conductively-doped semiconductor material.

The insulative cap 30 can comprise any suitable composition orcombination of compositions, and in some aspects can comprise, consistessentially of, or consist of one or both of silicon dioxide and siliconnitride. The cap 30 has an uppermost surface 31.

Although the gate dielectric 26, conductive material 28 and insulativecap 30 are all shown to be homogeneous, it is to be understood that theinvention includes aspects in which one or more of such structures cancontain two or more layers of differing composition relative to oneanother.

Sidewall spacers 32 are on opposing sidewalls of the gate stack. Thesidewall spacers can comprise any suitable composition or combination ofcompositions, and in particular aspects can comprise, consistessentially of, or consist of one or both of silicon dioxide and siliconnitride. The sidewall spacers have outer surfaces 33.

A pair of electrically conductive pedestals 34 and 36 extend verticallyfrom substrate 12, and are in electrical connection with source/drainregions 22 and 24, respectively. Pedestals 34 and 36 compriseelectrically conductive material 38 which can correspond to any suitablecomposition or combination of compositions. In some aspects, theelectrically conductive material 38 can comprise, consist essentiallyof, or consist of any of various metals, metal compositions, orconductively-doped semiconductor material. Although the material 38 ofthe pedestals is shown to be homogeneous, it is to be understood thatthe invention also includes aspects in which such material comprises twoor more layers having differing composition relative to one another.

The pedestals only cover portions of source/drain regions 22 and 24, andaccordingly such source/drain regions have surfaces 23 and 25,respectively, extending outwardly beyond the pedestals. Such surfacescan comprise, for example, conductively-doped monocrystalline silicon.

An electrically insulative material 40 is over substrate 12, and overtransistor 18. The pedestals 34 and 36 extend through such insulativematerial to electrically couple with the source/drain regions 22 and 24.

Electrically insulative material 40 can comprise any suitablecomposition or combination of compositions, and in some aspects cancomprise, consist essentially of, or consist of one or more ofborophosphosilicate glass (BPSG), phosphosilicate glass (PSG),fluorosilicate glass (FSG), silicon dioxide and silicon nitride.Although the material 40 is shown to be homogeneous, it is to beunderstood that the invention also includes aspects in which suchmaterial comprises two or more layers having differing compositionrelative to one another.

Construction 10 is shown to comprise a planarized upper surface 41extending across insulative material 40, and across pedestals 34 and 36.The pedestals 34 and 36 have upper surfaces 35 and 37, respectively,that are part of planarized surface 41.

Reflective properties of various materials of the FIG. 1 constructioncan be utilized during photolithographic patterning of a photoresistsubsequently formed over upper surface 41. The material 40 can be atleast somewhat transparent to electromagnetic radiation utilized duringthe photolithographic patterning so that the electromagnetic radiationreaches surfaces of the structures underlying material 40. Specifically,the electromagnetic radiation can reach one or more of upper surfaces17, 23, 25, 31 and 33. The upper surfaces 35 and 37 of the pedestals cancomprise metal, metal compounds, or other relatively highly reflectivecompositions; and the upper surfaces 17, 23, 25, 31 and 33 can comprisecompositions that are less reflective than those of surfaces 35 and 37.Accordingly, construction 10 can be considered to comprise a topographyimpacted by electromagnetic radiation directed downwardly towardconstruction 10, with such topography containing surfaces 17, 23, 25,31, 33, 35 and 37; and with surfaces 35 and 37 differing in reflectivityrelative to the other surfaces of the topography. In some aspects, thesurfaces 35 and 37 of the spaced pedestals 34 and 36 can be consideredto define a first region of construction 10 having relatively highreflectivity, and surfaces between the spaced pedestals can beconsidered to define a second region having low reflectivity incomparison to the first region.

If material 40 is not transparent to the electromagnetic radiationreaching such material, the topography impacted by electromagneticradiation directed downwardly toward construction 10 can be consideredto comprise upper surfaces of material 40 and the upper surfaces of thepedestals 34 and 36.

The construction 10 of FIG. 1 can correspond to a unit of an array ofrepeating structures. Accordingly, the transistor and pair of pedestalsof FIG. 1 can be representative of a number of identical structuresformed over substrate 12 at the processing stage of FIG. 1.

Referring to FIG. 2, a layer of material 42 is formed over upper surface41. Material 42 is ultimately to have a pattern formed therethrough todesignated portions of surface 41, and can comprise any suitablecomposition or combination of compositions. In typical aspects, material42 will be electrically insulative and will comprise, consistessentially of, or consist of one or more of BPSG, PSG, FSG, silicondioxide and silicon nitride. Although material 42 is shown to behomogeneous, it is to be understood that the invention also includesaspects in which material 42 comprises two or more layers havingdiffering composition relative to one another.

Material 42 can be understood to be formed over the topography discussedabove with reference to FIG. 1. Specifically, material 42 is formed oversurfaces 35 and 37 of the pedestals, and over surfaces between thepedestals.

An optically saturable absorption layer 44 is formed over material 42.Layer 44 comprises contrast enhancement material (also referred to asphoto-bleachable material) 46. The material 46 can comprise any suitablecomposition or combination of compositions, including, for example, oneor more contrast enhancement materials available from ShinMicroSI, Inc.of Phoenix, Ariz., with an exemplary contrast enhancement material beingCEM 365HR. Although only one optically saturable absorption layer isshown, it is to be understood that the invention can also includeaspects in which multiple optically saturable absorption layers areutilized.

In some aspects, the layer comprising material 42 can be considered tobe a first layer formed over underlying surfaces having differentreflectivity relative to one another, and the layer 44 can be consideredto be a second layer which is formed over the first layer.

Photoresist 48 is formed over optically saturable absorption layer 44.Although photoresist 48 is shown to be homogeneous, it is to beunderstood that the invention also includes aspects in which thephotoresist is not homogeneous. The photoresist can comprise anysuitable composition or combination of compositions, and can be either apositive photoresist or a negative photoresist.

The materials 42, 46 and 48 are incorporated into construction 10, andthe construction is then provided in an assembly 50 comprising a reticle52 (or photomask) and a source of electromagnetic radiation (not shown).

The reticle has radiation-patterning features formed therein. Suchfeatures comprise windows 54 and 56 through which electromagneticradiation can pass; and comprise non-transparent regions 58, 60 and 62which block the electromagnetic radiation.

Electromagnetic radiation 64 is emitted from the source and directedthrough the reticle, which patterns the electromagnetic radiation asshown. The patterned electromagnetic radiation is directed into thephotoresist 48.

Referring to FIG. 3, some of the electromagnetic radiation 64 passesentirely through the photoresist, and into construction 10. Suchelectromagnetic radiation is indicated by dashed lines in FIG. 3. Someof the electromagnetic radiation passing into construction 10 penetratesthrough materials 42 and 46. Such electromagnetic radiation can reachreflective surfaces 35 and 37 and be reflected (or bounced) back towardphotoresist 48 as indicated by arrows 65. Some of electromagneticradiation passing into construction 10 can also impact surfaces ofmaterial 40 adjacent the pedestals 34 and 36. Material 40 can be lessreflective than the material 38 of the pedestals, and accordingly canabsorb most of the electromagnetic radiation rather than reflecting it.

In the shown aspect, material 40 is somewhat transparent so that atleast some of the electromagnetic radiation reaching material 40 passesthrough the material to reach surfaces underlying material 40 (such as,for example, one or more of the shown surfaces 17, 23, 25, 31 and 33).

Some of the electromagnetic radiation reaching surfaces underlyingmaterial 40 is reflected back toward photoresist 48 as indicated byarrows 67. The arrows 67 are shorter than the arrows 65 to indicate thatin the shown aspect of the invention, the magnitude of reflection fromthe various surfaces underlying material 40 is less than the magnitudeof reflection from the upper surfaces 35 and 37 of pedestals 34 and 36.Such can result from the surfaces 35 and 37 being of more reflectivecompositions than the surfaces underlying material 40. In other words,the surfaces 35 and 37 can have a higher ratio of reflectance toabsorbance than the surfaces underlying material 40.

Referring to FIG. 4, the radiation 64 directed through photoresist 48,in combination with that reflecting back from surfaces 35 and 37 of thepedestals, alters transparency of segments 70 and 72 of material 46.Specifically, such segments receive a sufficient dose of the radiationto cause photo-bleaching of the photo-bleachable material 46. Themagnitude arrows 65 of FIG. 3 are not shown in FIG. 4 in order tosimplify the drawing, and instead the reflected radiation is shown asdashed-line arrows of radiation 64 directed from surfaces 35 and 37toward material 46. To the extent that any electromagnetic radiationreflects from surfaces other than the surfaces 35 and 37, such isinsufficient to substantially alter transparency of photo-bleachablematerial 46 (in other words, is insufficient to form photo-bleachedregions over such other surfaces analogous to the photo-bleached regions70 and 72 that are generated over surfaces 35 and 37).

In the shown aspect of the invention, the windows 54 and 56 of reticle52 form patterns of radiation which expose regions 80 and 82 of thephotoresist to the incoming radiation. Such regions are wider than theuppermost portions of pedestals 34 and 36. However, the radiationreflected back from surfaces 35 and 37 of the pedestals forms windows 70and 72 in photo-bleachable material 46 that are about the same widths asthe uppermost portions of the pedestals. Such aspect of the invention isshown to occur when utilizing on-axis radiation. It is to be understoodthat the invention also includes aspects in which off-axis radiation isutilized (not shown).

Referring to FIG. 5, the electromagnetic radiation directed into thephotoresist, together with electromagnetic radiation bouncing fromsurfaces 35 and 37 back through altered segments 70 and 72 of material46, causes portions 90 and 92 of the photoresist to be exposed to athreshold dose of radiation suitable for development of the resist.Other portions of the resist which receive no radiation, or whichreceive only the radiation directed into the photoresist and not theradiation reflected back to the photoresist, do not receive thethreshold dose. Such other portions are labeled as 94, 96 and 98 in FIG.5. The portions of resist 48 receiving the threshold dose can bereferred to as first portions, and the portions of resist 48 notreceiving the threshold dose can be referred to as second portions.

In the shown aspect of the invention, the portions 90 and 92 of resist48 that receive the threshold dose of radiation are directly overpedestals 34 and 36. Further, such portions have widths corresponding tothe widths of segments 70 and 72, and thus have widths smaller than thewidths 80 and 82 of the patterned radiation directed through reticle 52.Accordingly, reticle 52 can be considered to coarsely define locationsof resist 48 where a threshold dose of radiation will be provided, andmethodology of the present invention can be considered to utilizereflective properties of structures underlying the photoresist to moreaccurately define the locations where the threshold dose will beprovided. Methodology of the present invention can thus increaseaccuracy of alignment of an image pattern formed in photoresist overunderlying structures, relative to the alignment occurring throughutilization of photomask 52 alone. The present invention can thereforebe utilized to compensate for mask misalignment.

Referring to FIG. 6, construction 10 is shown removed from apparatus 50(FIG. 5), and after development to remove the portions 90 and 92 (FIG.5) of the photoresist 48 that had been exposed to the threshold dose ofradiation, while leaving the portions 94, 96 and 98 of the photoresistthat had not been exposed to the threshold dose of radiation. The shownaspect of the invention utilizes a positive photoresist, and accordinglythe portions exposed to the threshold dose of radiation are removed bythe development of the photoresist. The invention includes other aspects(discussed below with reference to FIG. 10) in which negativephotoresist is utilized, and accordingly the portions of photoresist 48which did not receive the threshold dose of radiation are removed by thedevelopment of the photoresist. Regardless, the portions of thephotoresist exposed to the threshold dose of radiation can be consideredto be first portions, and those not exposed to the threshold dose ofradiation can be considered to be second portions, and the developmentcan be considered to selectively remove either the first or secondportions relative to the other of the first and second portions.

The removal of the first portions of the photoresist forms gaps 100 and102 extending through the photoresist to the optically saturableabsorption layer 46. The gaps 100 and 102 are directly over pedestals 34and 36, respectively.

Referring to FIG. 7, the openings 100 and 102 are extended throughmaterials 42 and 46 with an appropriate etch, or combination of etches,to expose upper surfaces 35 and 37 of pedestals 34 and 36. In someaspects (not shown) the etching can extend into material 38, rather thanstopping precisely at surfaces 35 and 37.

Referring to FIG. 8, conductive material 104 is formed within openings100 and 102; and materials 46 and 48 (FIG. 7) are removed. Construction10 is shown comprising a planarized surface 103 extending acrossconductive material 104 and electrically insulative material 42. Suchplanarized surface can occur by, for example, over-filling openings 100and 102 with the conductive material, and subsequently removing excessconductive material by chemical-mechanical polishing. The materials 46and 48 can be removed before or after formation of conductive material104, and in some aspects can be removed by the chemical-mechanicalpolishing utilized to form planarized surface 103.

The conductive material 104 forms a pair of electrically-conductiveinterconnects 106 and 108 which are well-aligned with underlyingpedestals 34 and 36, respectively. Conductive material 104 can compriseany suitable composition or combination of compositions, and in someaspects can comprise, consist essentially of, or consist of one or moreof various metals, metal compositions and conductively-dopedsemiconductor material. Although material 104 is shown to behomogeneous, it is to be understood that the material can, in someaspects, comprise two or more layers of differing composition relativeto one another.

The interconnects 106 and 108 can be utilized for electricallyconnecting electrically-conductive pedestals 34 and 36 to circuitrywhich is ultimately desired to be electrically coupled with source/drainregions 22 and 24. For instance, FIG. 9 shows interconnect 106electrically coupled with a bitline 110, and shows interconnect 108electrically coupled with a charge storage device 112 (such as, forexample, a capacitor). As is known to persons ordinary skill in the art,a dynamic random access memory (DRAM) unit cell comprises a chargestorage device coupled to a bitline through a transistor. Accordingly,the structure of FIG. 9 can be considered to comprise a DRAM unit cell.A plurality of such structures can be simultaneously fabricated to forma DRAM array. The DRAM array can be incorporated into an electronicsystem, such as, for example, a system utilized in a computer, a car, aclock or an airplane.

The structure of FIG. 9 is but one exemplary structure which can befabricated utilizing methodologies of the present invention, and personsof ordinary skill in the art will recognize that the present inventioncan be applied to numerous other applications in which it is desired toaccurately photolithographically pattern photoresist.

The development of photoresist 48 discussed above with reference to FIG.6 showed removal of the regions of the photoresist which received thethreshold dose of radiation (regions 90 and 92 of FIG. 5). FIG. 10illustrates an alternative aspect of the invention in which thedevelopment removes portions of the photoresist which did not receivethe threshold dose of radiation (portions 94, 96 and 98 of FIG. 5). Suchremoval forms gaps 114,116, and 118 extending through the photoresist tomaterial 46, and leaves regions 90 and 92 of the photoresist asprojections between the gaps and directly over pedestals 34 and 36. Insubsequent processing analogous to that discussed above with referenceto FIG. 7, the gaps can be extended through layers 42 and 46, and intoor through material 40. Structures can then be formed within gaps, withexemplary structures being capacitor constructions which are ultimatelyto be incorporated into DRAM devices.

The processing discussed above with reference to FIG. 1 indicated thatsurfaces 35 and 37 had a different reflectivity than surfaces 17, 23,25, 31 and 33. In some aspects, the reflectivity of particular surfacesof a topography can be altered to enhance differences in reflectivity ofsome regions of the topography relative to other regions. FIG. 11 showsa construction 10 illustrating an exemplary application of such aspects.The construction of FIG. 11 comprises the pedestals 38 discussedpreviously with reference to FIG. 1, and the surfaces 17, 23, 25 and 33which were also discussed previously.

The construction of FIG. 11 differs from that of FIG. 1 in that upperregions of pedestals 34 and 36 are modified to form material 124. In anexemplary application, material 38 of the pedestals can comprise,consist essentially of, or consist of conductively-doped silicon; andmaterial 124 can comprise, consist essentially of, or consist of metalsilicide (for instance, titanium silicide) formed from the silicon ofthe pedestals.

The conversion of upper regions of the pedestals to metal silicide canenhance a difference in reflectivity of the surfaces 35 and 37 of thepedestals relative to one or more of the surfaces 17, 23, 25, 33 and 31.For instance, surfaces 23 and 25 of the source/drain regions cancomprise conductively-doped monocrystalline silicon, and such may have areflectivity too close to that of the silicon of the pedestals for someaspects of the invention. Accordingly, the upper regions of thepedestals can be converted to metal silicide to create a significantdifference in reflectivity between the upper surfaces of the pedestalsand the surfaces 23 and 25 of the source/drain regions. The constructionof FIG. 11 can subsequently be treated analogously to the processing ofFIGS. 2-9 to form interconnects extending to metal silicide material124.

Although the aspect of FIG. 11 is shown increasing reflectivity ofsurfaces, it is to be understood that the invention can also includeaspects in which one or more surfaces are treated to reduce reflectivityof such surfaces. Reduction of reflectivity of some surfaces can alsoenhance a difference in reflectivity between the treated surfaces andother surfaces.

FIGS. 1-9 and 11 illustrate aspects of the invention for formingelectrically-conductive structures extending to electricalinterconnects. Another aspect of the invention is for formingelectrically-conductive capacitor storage node structures. Such aspectis discussed with reference to FIGS. 12-17. Similar numbering will beused in describing FIGS. 12-17 as was used above in describing FIGS.1-11, where appropriate.

Referring to FIG. 12, such shows a construction 150 at a processingstage analogous to that discussed above with reference to FIG. 1. Theconstruction 150 comprises the substrate 12, isolation regions 14, andtransistor 18 discussed previously. The transistor 18 comprises the gatestack 20 having materials 26, 28 and 30 discussed above; and comprisesthe source/drain regions 22 and 24. The construction 150 furthercomprises the sidewall spacers 32 along sidewalls of the gate stack, andcomprises electrically insulative material 40 over the transistor 18 andthe substrate.

Construction 150 differs from the construction 10 of FIG. 1 in thatconstruction 150 comprises a short pedestal 152 extending fromsource/drain region 22 to a capacitor storage node 156. The pedestal 152comprises a material 154, which can be any suitable composition orcombination of compositions, including, for example, various metals,metal compositions, and conductively-doped semiconductor materials.Similarly, storage node 156 comprises a material 158 that can be anysuitable composition or combination of compositions, including thevarious exemplary compositions discussed above for material 154.

The storage node 156 is shaped as an upwardly-opening container, andaccordingly, in the shown cross-sectional view comprises a pair ofspaced pedestals 157 and 159. However, as is known to persons ordinaryskill in the art, the container-shape of storage node 156 would have acontinuous lateral sidewall when viewed from above, with the pedestals157 and 159 being part of that lateral sidewall. In particular aspects,the container sidewall would be circular or elliptical when viewed fromabove.

An electrically insulative material 160 is within the container openingof the storage node. Such material can be identical in composition tothe material 40, or can be different. In particular aspects, material160 can comprise BPSG, PSG, FSG, silicon dioxide and/or silicon nitride.

A planarized upper surface 161 is shown to extend across storage nodematerial 158, insulative material 40, and insulative material 160. Suchsurface can be formed by, for example, chemical-mechanical polishing.The material 160 comprises an upper surface 165.

Capacitor storage node 158 comprise an uppermost surface 163, andconstruction 10 also comprises surfaces 17, 23, 25, 31, 33 and 165adjacent the storage node. The surfaces 17, 23, 25, 31, 33,163 and 165can be considered to define a topography, with the surface 163 having ahigher reflectivity than the other surfaces of the topography. To theextent that surface 163 does not have sufficiently high reflectivityrelative to other surfaces of the topography, surface 163 and/or othersurfaces of the topography can be treated to increase the relativedifference in reflectivity between surface 163 and the other surfaces(with an exemplary treatment being analogous to that discussed abovewith reference to FIG. 11).

Referring next to FIG. 13, materials 42, 46 and 48 of the type discussedabove with reference to FIG. 2 are formed over surface 161. Material 42comprises an electrically insulative material, material 46 comprises anoptically saturable absorption layer, and material 48 comprisesphotoresist.

Referring next to FIG. 14, construction 150 is subjected tophotolithographic processing and development analogous to that discussedabove with reference to FIGS. 2-6. Such forms gaps 170 over surface 163.The gaps 170 are directly over reflective surface 163, as result oftaking advantage of the difference in reflectivity between surface 163and adjacent surfaces 17, 23, 25, 31, 33 and 165 duringphotolithographic patterning.

As discussed previously, storage node 156 would have a continuoussidewall comprising the projections 57 and 59 of the showncross-sectional view. Accordingly, surface 163 would extend entirelyaround such sidewall. The apparent pair of gaps 170 in thecross-sectional view of FIG. 14 would thus be a single gap having thesame lateral shape as the sidewall of the container-shaped storage node.However, in order to be consistent with the apparent pair of gaps in theshown cross-sectional views of FIG. 14 and the remaining figures,construction 150 will be referred to as having “gaps” 170, even thoughsuch gaps would actually be a single gap in the three-dimensionalstructure represented by the two-dimensional view of FIG. 14.

Referring to FIG. 15, gaps 170 are extended to surface 163 with anappropriate etch or combination of etches.

Referring next to FIG. 16, layers 46 and 48 (FIG. 15) are removed, andgaps 170 are filled with conductive material 172. Such conductivematerial can be identical to the conductive material 158, or different.Conductive material 172 extends the upwardly-opening capacitor storagenode through layer 42.

Referring to FIG. 17, materials 160 and 42 are removed from within thecontainer shape of the capacitor storage node, and subsequentlydielectric material 174 and capacitor plate material 176 are providedwithin the container shape of the capacitor storage node. The capacitorplate material is separated from storage node material 158 and 172 bydielectric material 174, but is capacitively coupled to such storagenode material.

The combination of the storage node, dielectric material and capacitorplate material forms a capacitor 178. Such capacitor is but oneexemplary capacitor that can be formed utilizing methodology of thepresent invention. In other applications, the dielectric material andcapacitor plate material can extend along the outside of the containershape as well is within the inside of the container shape. Also, inother applications the capacitor can be a pedestal-type capacitor ratherthan a container-type capacitor.

Source/drain region 22 is shown connected to a bitline 180 to form aDRAM unit cell comprising the capacitor 178 and transistor 18.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of patterning photoresist, comprising: forming an opticallysaturable absorption material over two or more regions of asemiconductor substrate, with at least two of the two or more regionsdiffering in reflectivity relative to one another; forming thephotoresist over the optically saturable absorption material; passingelectromagnetic radiation through the photoresist and to the regions; atleast some of the electromagnetic radiation that reaches the regionsbeing reflected off from at least one of the regions; the difference inreflectivity of the regions patterning the reflected electromagneticradiation; the directed electromagnetic radiation and patternedreflected electromagnetic radiation together exposing a first portion ofthe photoresist to a threshold dose of radiation while a second portionof the photoresist remains not exposed to the threshold dose; andselectively remove either the first or second portion of the photoresistrelative to the other of the first and second portions.
 2. A method ofpatterning photoresist, comprising: forming an optically saturableabsorption material over two or more regions that differ in reflectivityrelative to one another; forming the photoresist over the opticallysaturable absorption material; directing electromagnetic radiation intothe photoresist; some of the directed electromagnetic radiation passingthrough the photoresist and reflecting back from one or more of theregions toward the photoresist; the difference in reflectivity of theregions patterning the reflected electromagnetic radiation; the directedelectromagnetic radiation and patterned reflected electromagneticradiation together exposing a first portion of the photoresist to athreshold dose of radiation while a second portion of the photoresistremains not exposed to the threshold dose; and developing thephotoresist to selectively remove either the first or second portion ofthe photoresist relative to the other of the first and second portions.3. The method of claim 2 further comprising: forming a substance overthe regions, with said substance being at least partially transparent tothe electromagnetic radiation; and forming the optically saturableabsorption layer over the substance.
 4. The method of claim 3 whereinthe substance is electrically insulative.
 5. A method of patterningphotoresist over a semiconductor construction, comprising: forming thesemiconductor construction to have, in at least one cross-section, aplurality of spaced apart electrically conductive pedestals over asemiconductor substrate, and to have electrically insulative materialbetween the spaced apart electrically conductive pedestals; thepedestals having upper surfaces, and the electrically insulativematerial having an upper surface; forming an optically saturableabsorption layer over the upper surfaces of the pedestals andelectrically insulative material; forming the photoresist over theoptically saturable absorption layer; reflecting electromagneticradiation from the upper surfaces of the pedestals to optically alter asegment of the optically saturable absorption layer beneath thephotoresist and thereby increase transparency of such segment; directingelectromagnetic radiation into the photoresist; some of the directedelectromagnetic radiation passing through the photoresist, bouncing fromthe upper surfaces of the pedestals, through the altered segment of theoptically saturable absorption layer and into the photoresist; thedirected electromagnetic radiation and bounced electromagnetic radiationtogether exposing a first portion of the photoresist to a threshold doseof radiation while a second portion of the photoresist remains notexposed to the threshold dose; the first portion being directly over thepedestals, and the second portion being directly over the electricallyinsulative material; and selectively remove either the first or secondportion of the photoresist relative to the other of the first and secondportions.
 6. The method of claim 5 wherein the upper surfaces of thepedestals comprise metal.
 7. The method of claim 5 wherein the uppersurfaces of the pedestals comprise metal silicide.
 8. The method ofclaim 5 wherein the spaced apart pedestals are part of anupwardly-opening container.
 9. A method of forming a semiconductorconstruction, comprising: forming, in at least one cross-sectional view,spaced projections over a silicon-containing substrate; the spacedprojections having upper surfaces which are defined to be firstsurfaces; regions between the spaced projections having upper surfaceswhich are defined to be second surfaces; the first surfaces havinggreater reflectivity than the second surfaces; forming a first layerover the first and second surfaces; forming a second layer over thefirst layer, the second layer being an optically saturable absorptionlayer; forming photoresist over the optically saturable absorptionlayer; reflecting electromagnetic radiation from the first surfaces tooptically alter a segment of the optically saturable absorption layerbeneath the photoresist and thereby increase transparency of suchsegment; directing electromagnetic radiation into the photoresist; someof the directed electromagnetic radiation passing through thephotoresist, bouncing from the first surfaces, through the alteredsegment of the optically saturable absorption layer and into thephotoresist; the directed electromagnetic radiation and bouncedelectromagnetic radiation together exposing a first portion of thephotoresist to a threshold dose of radiation while a second portion ofthe photoresist remains not exposed to the threshold dose; developingthe photoresist to selectively remove either the first or second portionof the photoresist relative to the other of the first and secondportions and thereby form gaps in the photoresist selectively overdesignated regions comprising either the first surfaces or the secondsurfaces; and extending the gaps through the first and second layers andto the designated regions.
 10. The method of claim 9 wherein theprojections comprise conductively-doped silicon; wherein the uppersurfaces of the projections comprise metal silicide formed over thesilicon; wherein the designated regions comprise the first surfaces; andfurther comprising forming conductive material within the gaps toelectrically connect with the electrically conductive projections. 11.The method of claim 10 wherein the projections include pairedprojections having a transistor gate stack between them, wherein thesecond surfaces include a surface of an insulative cap of the insulativegate stack; and wherein the insulative cap surface comprises one or bothof silicon dioxide and silicon nitride.
 12. The method of claim 10wherein the first layer is electrically insulative.
 13. The method ofclaim 9 wherein the projections are electrically conductive, wherein thedesignated regions comprise the first surfaces, and further comprisingforming conductive material within the gaps to electrically connect withthe electrically conductive projections.
 14. The method of claim 13wherein the electrically conductive projections and conductive materialtogether are incorporated into at least one capacitor storage node, andfurther comprising: forming dielectric material along said at least onecapacitor storage node; and forming capacitor plate material spaced fromsaid at least one capacitor storage node by the dielectric material andcapacitively coupled with the at least one capacitor storage node. 15.The method of claim 14 wherein the at least one capacitor storage nodeis shaped as upwardly-opening container; and wherein the dielectricmaterial and capacitor plate material extend into the opening of theupwardly-opening container.